I got too occupied in exploring the other areas then the beta ended. I saw a YouTube video where these 2 guys went back there there was a whole huge area there...if I can only go back I could have explored a bit more...
Edit 1) found a video in the end of the video he's in there
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saw the same video in the beta. tried to go back whit lvl 8 nearly at the end of the beta, but the gate - that the ghost opened in the first mission, was closed again, so there was no way to go back to the outside of the wall....